Combined wireless sending and receiving system



1927. Jan 25 A. NYMAN COIBINED WIRELESS SENDING AND RECEIVING SYSTEM 2Sheets-Sheet .1

Original Filed July 15. 1920 M W W INVENTOR Alexander Afilman BY AA.TTORNEY vvvvvvv Jan. 25, 1927. 1,615, 645

A. NYMAN COMBINED WIRELESS SENDING AND RECEIVING SYSTEM Original FiledJuly 15. 1920 2 Sheets-Sheet 2 Jzlicrqpm WITNESSES: INVENTORAlexaader/fi/man 0' 73M 4 ATTORNEY ALEXANDER NYMAN, OI! WILKINSBURG,

PATENT OFFICE.

PENNSYLVANIA, ASSIGNOR TO WESTING- HOUSE ELECTIBIIC & MANUFACTURINGCOMPANY, A CORPORATION OF PENNSYL- VAN IA.

COMBINED WIRELESS SENDING AND RECEIVING SYSTEM.

Application filed July 15, 1920, Serial No. 896,530. Renewed January 28,1926.

My invention relates to the sending and receiving of wireless signals bymeans of changing the lengths of the transmitted waves.

More particularly, my invention relates to a system for wireless sendingand receiving of messages in which the transmitted wave is caused tovary in length 1n accordance with sound vibrations that are impressedupon the sending-circuit to vary the length of the transmitted wave.

An object of my invention is to provide a method for the transmissionand receipt of wireless signals, where the transmitted wave is varied inlength in accordance with the variations in the value of reactance,corresponding to sound "vibrations in the transmitting circuit and inwhich the receiving station is tuned to a frequency slightly above orbelow the average sending frequency, so that an increase or reduction inthe sending frequency will either increase or reduce the strength of thecurrent flowing in the receiving circuit. 1

Another object of my invention 18 to provide simple and practlcable aparatus that will be especially adapted for c anging the length of thetransmitted wave in accordance-with the voice vibrations.

One of the problems of wireless telegraphy has always been to, in somemanner, transmit signals of audible frequency impressed upon waves ofradio frequency. The radio-frequency waves have often periods less than1/500,000 of a second and, as this is far beyond the range ofaudibility, it is neccessary to transmit, in some manner, vibrations ofapproximately 1/1000 of a second or less so that the car can catch thesignal sent. To achieve this result, it has been customary to vary theamplitude of the radio-frequency vibrations in accordance withaudio-frequency vibrations, such as the voice. The voice waves were soimpressed upon the radio waves that they formed an envelope that boundedthe radio waves and restricted their amplitude to correspond to thevoice waves. Thus, every audible signal was composed of 'a plurality aof radio waves of an amplitude restricted in accordance with an envelopecorresponding to the voice vibrations.

The customary system of wireless transmitting and receiving by varyingthe amplitude of the transmitted wave has caused considerable diflicultyin large-power, wireless-telephone transmitting stations, for thepresent practice is to modulate the amplitude of the oscillations byinserting a microphone transmitter in some part of the sending circult.Such microphones must, of necessity, handle a large amount of power andtheir design is difficult and their operation inefiicient. By my schemeof varying the frequency 1n accordance with voice vibrations by the useof a new type of microphone, which modulates the frequency instead ofthe amplitude smaller power need be handled and the efficiency ofoperation may thereby be greatly increased.

The'method which I preferably employ to carry out my invention is tovary the reactance in the transmittin circuit by changmg the value ofeither 1n uctance or capacitance in accordance with voice vibrationsimpressed upon a vibrating member, such as a microphone diaphragm, andto tune the receivin station a little .above or a little below teaverage sending frequency, so that, at the receiving station, thestrength of current flowing through the receiving circuit willcorrespond to the changes in amplitude employed in the present type ofoscillations.

The amplitude may be modulated to a certain extent if the sendingcircuit has more than one defined frequency but this phenomenon ismerely incidental and in no wise interferes withthe application of theprincipleof my invention. Again, in employing high-frequency generators,the supply frequency is absolutely definite. In such a case, thefrequency of the oscillating circuit would be arranged to be a littleabove or a little below the supply frequency. The modulation offrequencies caused by the variations in value of the transmittingreactances will then either bring the oscillating circuit into resonanceor throw it further off from resonance. Changes in transmittingfrequency may be, in this case, quite inappreciable but, instead, theamplitude of oscillations will be affected; in other Words, theoscillations transmitted will be approximately of the same nature as theoscillations in present use in wireless teleg raphy. In this case, itmaybe advisable to .in the circuit. Fig. 4 diagrammatically illustrates,on a greatly exaggerated scale, the type of wave produced in the use ofmy invention. Fig. 5 is a diagram illustrating the application of myinvention to a transmitting circuit employing a high-frequencygenerator. Fig. 6 is a diagram illustrating my invention-as applied to acircuit having a changeable reactance operated by :1. vibratingelectro-magnet device that carries .the plate current of a vacuum tube,acting as an amplifier, the grid of which is subject to audiooscillations. Fig. 7 shows, diagrammatically, a device for varying thewave length by changing the magnetic flux within an induction coil. Fig.8 diagrammatically illustrates a device-for changing the inductancewithin a circuit by varylng the length of an induction coil inaccordance with audio vibrations. Fig. 9 diagrammatically shows a formof apparatus for changing the inductance in a circuit by varying thenumber of turns of a coil in accordance with audio vibrations.

Referring particularly to Fig. 1, there is indicated an antenna 1,connected to a variable inductance 2, and, through a variablecapacitance 3, to the ground. This forms the main antenna circuit. Ashunt circuit containing avariable inductance 4, a variable capacitance5, and a variable reactance mechanism 6, is shunted across the variablecapacitance 3 of the main antenna circuit. This shunt circuitconstitutes the circuit for changing the wave length of the sentoscillations, and the operation of the variable reactance mechanism 6will be more fully explained with reference to Fig. 3, which isillustrative of one type of mechanism that I employ.

Connected to the main antenna circuit is a" Poulsen-arc generator.- ofradio-frethe are by means of a generator 8, or by quency current, havingtwo are electrodes Power is supplied to-the, electrodes of any othersuitable source of constant current. One. of the arc electrodes isconnected to one generator terminal through a variable resistance 9 anda chokecoil 10. The variable resistance 9 controls the power delivery tothe arc, and the choke coil 10 protects the generator from inducedhigh-potential and high-frequency currents from the arc and antenna. Theother electrode of the arc is connected to the other terminal of thegenerator through a choke coil 11 that serves the same purpose as thechoke coil 10 and through coils 12 and 13 of an electro-Inagnet that hasits field concentrated across the are for the purpose of deionizing thegap to produce rapid extinction of the are upon fall of-the current, asis customary in 'Poulsen-arc transmitters.

The operation of the variable reactance mechanism 6, which will be morefully explained, causes the value of the reactance in the antenna shuntcircuit to vary in accordance with voice vibrations. This circuithandles but a small portion of the total power but the variation offrequency is sufficient to throw the receiver off resonance. even. atextremely small values, say V of 1%, so that a small variation of say10% in the shunt-circuit capacity, which handles 10% of the oscillatingpower, will be a satisfactory value. To reduce the voltage in the shuntcircuit to a suitable value, the

variable condenser 5 properly limit this voltage.

The action of the variable-reactance mechanism Will be apparent from aninspection of the construction shown in Fig. 3, which is a diagrammaticview of a form of device for varying the capacitance in accordance withvoice vibrations. There is illustrated a microphone having a mouth piece30 and a vibrating diaphragm 31. Attached to the mouth piece 30 'is asupport 32, a link 33 being attached to the center of the diaphragm 31of the microphone. The link 33 is attached to the mid-portion ofcondenser plates 34, as indicated by numerals 35. The condenser plates34 are attached to the support 32 that is fastened to the mouth piece30. These plates 34 are of a peculiar construction'in that the edges arebent to form inwardly-projecting faces of metal parallel to the mainface of the plates, as indicated at 36. The condenser plates 34 areassumed, for purposes of description, to have positive potential appliedto them. A second support 37 carries a second series of condenser plates38, carrying the negative potential, that are provided with apertures39, and to which link 33 is also attached without making electricalcontact.

may be adjusted to- The construction of the plates 38 is like thatpreviously described in the discussion of the condenser plates 34.

In operation the voice causes the diaphragm 31 to vibrate and this, byreason of the connection of the diaphragm 31 to the plates 34 and 38,causes them to vibrate, whereby the distances between them are varied tovary the capacitance of the device.

Since this device is located within a circuit carrying transmittingoscillations, the period of oscillation of the circuit is changed inaccordance with the variation in the capacitance, and the frequency ofthe transmitting waves is varied in accordance with voice vibrations.

In Fig. 2 is shown a receiving. station hav- 5 ing an antenna circuitcontaining an antenna capacitance 18 and a stopping condenser 19.-

An electron tube 20, acting as a detector,

, having a. grid element 21. a plate element 22 and a filament element23, is in circuit with .the inductance 17; In circuit across thecondensers 18 and 19 is a resistance '24 that performs the function ofthe customary grid leak in grid circuits of tubes used as de- 20tectors; To heat filament 23 I provide an A battery 25. The amount ofcurrent flowing from the filament 23 'is controlled by the insertion ofa variable resistance 25'.

Within the plate circuit of the electron tube 25 20 are locatedtelephone receivers 26 having a capacitance 27 shunted between them.

suitable B battery 28 applies positive potential to the plate 22. i

The received impulses induce oscillations in the inductance 17 by reasonof its inductive coupling to the inductance 15. ThlS induced currentacts to affect the potential of the grid 21 0fthe electron tube 120.and,

as proper conditions for the use of this tube 20 as a detector arepresent, oscillations'are set up in the plate circuit corresponding tothe received oscillations, andmessagesmay be taken through the telephonereceivers 26.

By virtue of the adjustment of the variable capacitance 18, the circuitmay be tuned to any desired frequency. f

t is obvious that any method of detecting the received oscillations maybe employed and that I have shown an electron tube used as a detector ofradio frequency solely for the purpose of illustration and to make clearthe utility of my invention and its application to the problems of radiocommunication.

The antenna and receiving circuits of the receiving station are tuned toa frequency slightly above or below' the average frequency sent from thetransmitting station. Therefore, an increase or reduction in sendingfrequency will either increase or reduce the strength of current flowingthrough the receiving circuit, and the detector in the receiver circuitwill correspond ,to the changes in the amplitude of the present'type ofoscillations. Audio signalswill be caught in the telephone receivers 26in accordance -with I the fluctuation in frequency of the transmittedwave. I

In. Fig. 4 is diagrammatically illustrate d on a greatly exaggeratedscale, the shape of atrain of waves sent outfrom the transmittingstation. The axis upon which the waves are propagated is the axisindicating Time? It is apparent that the frequency, which is areciprocal of the Time, varies inversely as. the length of the wave.Such a wave train is propagated by a transmitting station of the typeshown in Fig. 1, having a capacity-varying mechanisni,such as isillustrated in Fig. 2.

' In Fig.5 is shown an application of theprinciples of my invention to acircuit containing ,a high-frequency alternator. of the common type. Inthis( circuit, an antenna 50, a variable inductance 51 and a variablecapacitance 52 constitute the .main antenna circuit. Shunted across thevariable capacitance 52 is a shunt circuit having a variable inductance54, a variable capacitance 55 and a reactance-varying mechanism 53,which may be of the type previously described-in referring to Fig. 3. A'highfrequency alternator 56 is provided, through Y which power isdelivered to the main .antenna circuit.

In a high-frequency alternator, the supply frequency isabsolutelydefinite. It has been found advisable to tune the receiver tothe average sending frequency, for the (hanges in the transmittingfrequency may, in this case,.be quite unappreciable. but, instead, theamplitude of oscillations will be affected. The frequency of theoscillating circuit should be arranged to be a little above or a littlebelow the frequency desired, then the modulations of frequency caused bythe transmitting inductance will either brine: the antenna into, orthrow it further off from, resonance. In using this type of aparatus,therefore, the amplitude of oscilations is affected, rather than thefrequenc and the transmitted oscillations will be approximately of thesame ntfture as has heretofore been customary in wireless telephony. InFig. 6 is shown apparatus of a suitable :type foraccomplishingamplification. The

antennacircuit comprises an antenna 60, a variable inductance 61 and avariable capacitance 62, through which the circuit is connected to theground. The main sending inductance is indicated by the inductance63,through which radio oscillations of constant frequency are supplied tothe antenna. A shunt circuit, connected across the inductance 61,contains a-variable-reactance mechanism 64 for varying the period ofvibration of the shimt circuit. Operatively connected to themoving'parts of the variablereactance mechanism 64, is a link 65 that isattached to the middle of a flexible metal diaphragm 66. A microphone67, having a battery 67 and aninductance 68 in circuit therewith,constitutes a microphone transmitter. An inductance coil 69 isinductively coupled to the inductance 68 and constitutes the secondaryof an audio-f uency transformer, the rimary of which is the, inductance68. T 1e inductance 69is coupled to the grid 70 of an electron tube 71,oper ating as an amplifier and having a plate 7:2 and a filament 73. Toheat the filament, a battery 74 is provided, the current from whichpasses through a variable resistance 75 to the filament. \Vithin theplate circuit of this electron tube 71 is a B battery 76 and anelectro-magnet 77 that is adapted to actuate the vibrating diaphragm-66.

The operation of this amplifier is as follows: The voice produces, inthe micro phone circuit, fluctuations of current that, in turn, areimpressed upon the grid 70 of the electron tube 71, and, since thecondition for the tube 71 to o erate as an amplifier are present,amplified audio oscillations are induced in the plate circuit (if thistube, and the electro-magnet 77 causes the diaphragm 66 to vibratestrongly in accordance with of the diaphragm,

these changes in current. Great amplification of the fluctuation ofreactance Within the shunt circuit of the antenna is obtained, so that aweak sound will produce a large reactance change in the shunt circuit ofthe antenna, and hence, greater variation of frequency in the antennaoutput than a loud sound would produce under ordinary conditions.

In -Fig. 7, a type of device for yarying the transmitting circuitreactance within the is diagrammatically illustrated, in which thecircuit is varied. A mouth piece 80, in operative relation to adiaphragm 81 that is ada ted to vibrate in accordance with voice virations, has a lug of magnetic-metal 82 fastened at its center. Themetal lug 82, preferably of iron, is adapted to pass within the interiorof-hn induction coil 83 that carries the current in the circuit. Whenthe voice causes the diaphragm 81 to vibrate, the position of the lug 82within the interior of the induction coil 83 changes, and hence, the magnetic flux within the coil is changed, time varying the inductance inthe circuit, and, consequently, the frequency of oscillation.

Another type of apparatus is shown diagrammatically in Fig. 8 of thedrawings, in which is direct sounds u central point .8 end of a helicalon a dia hragm-86, at'the. of whic1 is attached one spfing 88constituting an inductance. Upon speaking within the mouth piece, thediaphragm 86 vibrates and causes the spring 88 to be shortened andlengthened in accordance with theposition so that the inductive value ofthe spring is changed in accordance with voice vibrations, and hence,the frequency of the-circuit including this devi a is varied.

In Fig. 9 is diagrammatically illustrated yet another type ofreactance-varyi'ng meched to the understood that such a provided a mouthpiece 85 to anism in which the inductance is changed by varying thenumber of turns duction (3011- A mouth piece 90 is here indicated inoperative relatlon to a diaphragm 91, ,having'attached, at its centralpoint 92, one end of a coiled-wire spring 93 the other end of which isjoined, at point 95, to one of the main terminals of the circuit. Thecoil-wire spring 93 is fastened, at a point 94, to the other terminal ofthe cirquit, and, likewise, at the point 95, to a stationarynonconductor indicated at 96. Since the wire 93 is of spring materialthevibration of the diaphragm 92 causes it to readily conform to thevibrations, and the effective number of turns of inductance is changedin accordance with the voice vibrations, so that the period ofoscillation of the circuit including the device is varied.

While I have shown several devices for varying the reactance Within thetransmit ting circuit to change the oscillating frequency in accordancewith voice vibrations, I wish it to be expressly understood that anymethod by which the same result may be accomplished will lie Within thespirit of my invention, and I do not wish to be limitparticularconstructions which I have shown.

Since the period of vibration is controlled by varying the reactance inthe circuit, it

makes no difference whether the inductance or the capacitance bechanged. Either inductance or capacitance may be varied and it may befound advisable to vary the values of both inductance and capacitance'inthe circuit simultaneously, and I wish it to be templated as lyingwithin the scope of this invention. I

While I have described but one embodiment of my invention, manymodifications may be made therein by those skilled in the art withoutdeparting from the spirit thereof, and I desire, there-' fore, that myinvention be limited only as set forth in the appended claims or by theshowing of the prior art.

I claim as my invention:

1. In a system for the transmission of intelligence, the combinationincluding a source of high-frequenc carrier waves of substantiallyconstant requency, a tuned circuit including in" series a portion of aninductance device and a capacitance device, means for connecting saidsource across said capacitance device and a portion of said inductancedevice, and a sound-responsive variable reactance element shunting oneof said dveices.

2. In a system for the transmission of intelligence, the combinationincluding a source of high-frequency carrier waves of substantiallyconstant frequency, a capacitance device, an inductance device in seriesof an in it is apparent thatv llm construction is .con- 1 llii ' ticallymoved conductive; member capable 3. The combination with a source ofoscillatory currents, of a tuned circuit energized thereby and lncludinga coil, and an acousof setting up eddy currents inductively inductancethereof.

4: The combination with a sourceof highfrequency currents, and a tunedcircuit energiz'ed. thereby and including a coil, of a metallic memberprojecting axially into said coil and acoustic means for moving saidmember-to cause it to be more or less inductively associated with saidcoil to vary the tuning of said circuit.

5. The combination with a source of highfrequency currents, and a tunedcircuit ener-' gized thereby and including a coil, of a magnetic memberprojecting axially into said tially coil and acoustic means for movingsaid member whereby it projects into said coil to a greater or lessdistance and thereby alters the impedance of said coil to vary thetuning of said circuit.

6. In a system for wireless transmission of signals, means formodulating the transmitted wave comprising a member vibrating accordingto audio impulses, an-induction coil associated with the transmittingcircuit and an iron core within the induction coil and extending partway along the axis of said coil and connected to the v1brating member tovary the amount of inductance within the transmitting circuit.

7 In a radio sending system, a'radiating circuit including an aerial, anadjustable inductor, an adjustable condenser and a ground, a source ofhigh-frequency current connected around said adjustable condenser and anadjustable portion of said adjustable inductor, and a shunt aroundsaidadjustable condenser, said shunt including an adjustable inductor,an adjustable condenser and an acoustically varied reactor in series,whereby said shunt may be adjusted nearly to resonance at the frequencyof said source, the antenna may be adjusted to radiate energy from saidsource when said shunt is non-resonant, and the acoustically variedreactor will then pause modulation of the radiations.

8. In a system for the transmission of intelligence, the combination ofa source of high-frequency carrier waves of substanconstant frequency, atune'd circuit including tuning devices external to said Source andtuned thereby to a frequency ance with the signals to be transmitted.

9. In a system for the transmission of intelligence, the combination ofa source of high-frequency carrier waves of substantially constantfrequency, a tuned circuit ineluding tuning devices external to saidassociated with said coil for varying the.

materially affect the frequency of the oscillations, and means includinga coil having a movable metallic core for varying the tuning of saidlast-mentioned circuit, whereby the amplitude of the oscillations may bevaried in accordance with the signals to be transmitted.

11. In a system for the transmission of intelligence, the combination ofa source of high-frequency carrier waves of substantially constantfrequency, a tuned circuit including tuning devices external to saidsource and tuned thereby toa fre uency near that of said carrier waves,where y the a pitude of said carrier waves will be depe dent' upon thenearness of said frequencies, and reactance means shunting a sin le oneof said tuning devices for varying t e naturalperiod of said tunedcircuit in accordance with the signals to be transmitted, said tunedcircuitbeing normally slightly detuned from the condition of exactresonance.

12. An oscillation generator comprising two or more tuned circuits, oneof said circuits being such that its tuning does not materially afiecljthe frequency of the oscillations, and means including a coil having amovable. metallic core for varying the tuning of said last-mentionedcircuit, whereby the amplitude of the oscillations may be varied inaccordance with the signals to be transmitted, said last-mentionedcircuit being normally slightly detuned from the condition of exactresonance to said oscillations.

In testimony whereof, I have hereunto subscribed my name this 10th dayof July 1920.

AL XANDER NYMAN.

